The surfaces of polymeric materials have been modified previously. See, for instance, Braybrook et al., Prog. Polym. Sci. 15:715-734 (1990). Previous research principally has been directed to developing novel composites [Baum et al., Chem. Mater. 3:714-720 (1991)] biosensors [Pantano et al., J. Am. Chem. Soc. 113:1832-1833 (1991)] and biomaterials [Allcock et al., Chem. Mater. 3:450-454 (1991)]. Surface modification also has been combined with photolithography to spatially direct the synthesis of peptides or oiigonucleotides, Fodor et al., Science 251:767-773 (1991) and Kiederowski, Angew. Chem. Int. Ed. Eng. 30:822-823 (1991); and immobilization of biopolymers. Rozsnyai et al., Angew. Chem. Int. Ed. Eng. 31:759-761 (1992). Most of the surface modification processes known in the art involve sequential treatment of surfaces with chemical reagents, Id., and only a few such studies have involved the use of azides as surface-modification reagents. Breslow, in Scriven (ed.) Azides and Nitrenes, chapter 10, Academic Press, New York (1984); Harmer, Langmuir 7:2010-2012 (1991).
Examples of existing methods for modifying polymer films include sulfonation of polystyrene, Gibson et al., Macromolecules 13:34 (1980); sulfonation of poly(aryloxy)phosphazenes, Allcock et al., Chem. Mater. 3:1120 (1991); plasma treatment of polyester, Porta et al., Chem. Mater. 3:293 (1991); base hydrolysis of polyimide, Lee et al., Macromolecules 23:2097 (1990); base hydrolysis of polyphosphazenes, Allcock et al., Chem. Mater. 3:1441 (1991); and base treatment of poly(vinylidene fluoride), Dias et al., Macromolecules 17:2529 (1984).
Another conventional method for modifying polymers comprises exposing the surface of a hydrocarbon polymer such as polyethylene with nitrene or carbene intermediates generated in the gas phase. Breslow, in Scriven (ed.), Azides and Nitrenes, chapter 10, Academic Press, New York (1984). Also, difluorocarbene generated in solution has been reported to modify 1,4-polybutadienes. Siddiqui et al., Macromolecules 19:595 (1986).
Perfluorophenyl azides (PFPAs) have been shown to exhibit improved CH-insertion efficiency over their non-fluorinated analogues when the PFPAs were photolyzed in hydrocarbon solvents such as cyclohexane or toluene. Keana et al., Fluorine Chem. 43:151 (1989); Keana et al., J. Org. Chem. 55:3640 (1990); Leyva et al., J. Org. Chem. 54:5938 (1989); and Soundararajan et al., J. Org. Chem. 55:2034 (1990). PFPAs were initially developed as efficient photolabeling reagents. Cai et al., Bioconjugate Chem. 2:38 (1991); Pinney et al., J. Org. Chem. 56:3125 (1991); and Crocker et al., Bioconjugate Chem. 1:419 (1990). Recently, bis-(PFPA)s have been shown to be efficient cross-linking agents for polystyrene, Cai et al., Chem. Mater. 2:631 (1990); and poly(3-octylthiophene), Cai et al., J. Molec. Electron. 7:63 (1991).
Molecular imprinting methods also are known. See, for instance, Molecular Imprinting, Macromol Chem., 187:687 (1981). Molecular imprinting creates specific recognition sites in materials, such as polymeric organic materials. Known molecular imprinting techniques involve crosslinking materials in the presence of a functional monomer or mixture of monomers. The imprinting molecule interacts with a complementary portion of a functional monomer, either covalently or by other interactions such as ionic, hydrophobic or hydrogen bonding, so that recognition sites for the imprinting molecule can be provided in the substrate material. The imprinting molecule is then removed from the substrate to leave the recognition site. Some of these imprinting methods have been patented. For instance, Mosbach's U.S. Pat. No. 5,110,883 describes the preparation of synthetic enzymes and synthetic antibodies by molecular imprinting techniques.
Previous methods have failed to provide molecularly imprinted thin, substantially defect free films that can be used for the manufacture of sensor devices. Most known techniques begin with monomeric materials that are polymerized during the imprinting process. It has proven virtually impossible to control the production of acceptably thin films by these known processes.
Sensors ostensibly designed for medical applications, currently are receiving considerable attention. The methods used for detecting analytes with such sensors are many and varied. See, for instance, Janata et al.'s Anal. Chem., 66:207 (1994). Molecular imprinting recently has been shown to be a useful means for sensing the presence of certain materials. Mosbach, Trends Biochem. Sci., 19:9 (1994). However, the limitations imposed on the thickness of the film and the defects provided therein by known methods have substantially limited the capability to use such materials for the detection of plural analytes using a single sensor.